In recent years, a demand for hair coloring has increased, and the market of hair coloring has been extended more and more, as is called a “hair coloring boom”.
Depending upon the types of dye components used, however, the colored hair has a problem that change of hue (discoloration) occurs because a part of dye compounds having undergone oxidation polymerization inside hairs are washed away in a biased ratio by hair washing and a problem that lightness of the hair tends to increase and the color is not long-lasting (color fading is liable to occur) because dye compounds having undergone oxidation polymerization inside hairs are washed away from hairs in a relatively short period of time. Problems of such discoloration and color fading are conspicuous especially when hair is colored a color tone having a medium or higher lightness (e.g., brown).
In connection therewith, in a patent document 1, an oxidation color development type black coloring agent containing, as active ingredients, 4,4′-diaminodiphenylamine, 1-naphthol, resorcin and m-aminophenol in given amounts is disclosed, and with regard to hair having been colored with the black coloring agent, color fastness to sunlight, potash soap and sweat has been studied. In the patent document 1, however, discoloration and color fading in other cases than the case where white or gray hair is colored black have not been studied, and also the color fastness having been studied is desired to be secured over a longer period of time.
In a patent document 2, a hair coloring agent composition comprising (a) one or more components selected from p-phenylenediamine, toluene-2,5-diamine and the like, (b) o-chloro-p-phenylenediamine or a water-soluble salt thereof and (c) α-naphthol is disclosed, and it is described that resorcin, m-aminophenol and o-aminophenol may be contained as arbitrary components. However, specifically disclosed as an embodiment containing α-naphthol is a hair coloring agent composition comprising 2,5,6-triamino-4-hydroxypyrimidine sulfate and α-naphthol or comprising these components and o-chloro-p-phenylenediamine sulfate, and with regard to a hair bunch having been colored with the composition, fastness to light is evaluated, but change of hue (discoloration) and color fading due to hair washing are not mentioned at all.
In a non-patent document 1, there is disclosed a hair coloring agent composition containing (a) one or more dye intermediates selected from p-phenylenediamine, toluene-2,5-diamine, 4,4′-diaminodiphenylamine, p-aminophenol, o-chloro-p-phenylenediamine and the like in an amount of 0.01 to 10% by weight and (b) one or more couplers selected from resorcin, α-naphthol and the like in an amount of 0.01 to 10% by weight, wherein the weight ratio of the dye intermediate (a):the coupler (b) is in the range of 1:10 to 10:1. In the non-patent document 1, however, color fastness (resistance to change in color and color fading) of the hair coloring agent composition is not studied at all.
Accordingly, there has been eagerly desired development of a hair coloring agent composition which hardly causes change of hue, brings about slow fading of a color and provides a long-lasting color even if hair washing is repeated after the hair coloring agent composition penetrates into hairs and develops a color.
Patent document 1: Japanese Patent Publication No. 43722/1990
Patent document 2: Japanese Patent Laid-Open Publication No. 173039/1995
Non-patent document 1: Journal of Technical Disclosure No. 15922/1995 issued by the Japan Institute of Invention and Innovation